/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
 
package datafu.pig.sets;

import org.apache.pig.EvalFunc;
import org.apache.pig.data.DataBag;
import org.apache.pig.data.DataType;
import org.apache.pig.impl.logicalLayer.schema.Schema;

/**
 * Base class for set operations.
 */
public abstract class SetOperationsBase extends EvalFunc<DataBag>
{
  @Override
  public Schema outputSchema(Schema input)
  {
    try {      
      for (Schema.FieldSchema fieldSchema : input.getFields())
      {
        if (fieldSchema.type != DataType.BAG)
        {
          throw new RuntimeException("Expected a bag but got: " + DataType.findTypeName(fieldSchema.type));
        }
      }
      
      Schema bagSchema = input.getField(0).schema;
                  
      Schema outputSchema = new Schema(new Schema.FieldSchema(getSchemaName(this.getClass()
                                                             .getName()
                                                             .toLowerCase(), input),
                                           bagSchema,
                                           DataType.BAG));
            
      return outputSchema;
    }
    catch (Exception e) {
      return null;
    }
  }
}
